# encoding: UTF-8

require "base64"
require "redis"

require File.join(File.dirname(__FILE__), "ohm", "validations")
require File.join(File.dirname(__FILE__), "ohm", "compat-1.8.6")
require File.join(File.dirname(__FILE__), "ohm", "key")
require File.join(File.dirname(__FILE__), "ohm", "collection")

module Ohm
  VERSION = "0.0.37"

  # Provides access to the Redis database. This is shared accross all models and instances.
  def redis
    threaded[:redis] ||= connection(*options)
  end

  def redis=(connection)
    threaded[:redis] = connection
  end

  def threaded
    Thread.current[:ohm] ||= {}
  end

  # Connect to a redis database.
  #
  # @param options [Hash] options to create a message with.
  # @option options [#to_s] :host ('127.0.0.1') Host of the redis database.
  # @option options [#to_s] :port (6379) Port number.
  # @option options [#to_s] :db (0) Database number.
  # @option options [#to_s] :timeout (0) Database timeout in seconds.
  # @example Connect to a database in port 6380.
  #   Ohm.connect(:port => 6380)
  def connect(*options)
    self.redis = nil
    @options = options
  end

  # Return a connection to Redis.
  #
  # This is a wapper around Redis.new(options)
  def connection(*options)
    Redis.new(*options)
  end

  def options
    @options || []
  end

  # Clear the database.
  def flush
    redis.flushdb
  end

  def key(*args)
    Key[*args]
  end

  module_function :key, :connect, :connection, :flush, :redis, :redis=, :options, :threaded

  Error = Class.new(StandardError)

  class Model

    # Wraps a model name for lazy evaluation.
    class Wrapper < BasicObject
      def initialize(name, &block)
        @name = name
        @caller = ::Kernel.caller[2]
        @block = block

        class << self
          def method_missing(method_id, *args)
            ::Kernel.raise ::NoMethodError, "You tried to call #{@name}##{method_id}, but #{@name} is not defined on #{@caller}"
          end
        end
      end

      def self.wrap(object)
        object.class == self ? object : new(object.inspect) { object }
      end

      def unwrap
        @block.call
      end

      def class
        Wrapper
      end

      def inspect
        "<Wrapper for #{@name} (in #{@caller})>"
      end
    end

    class Collection
      include Enumerable

      attr :raw
      attr :model

      def initialize(key, model, db = nil)
        @model = model.unwrap
        @raw = self.class::Raw.new(key, db || @model.db)
      end

      def <<(model)
        raw << model.id
      end

      alias add <<

      def each(&block)
        raw.each do |id|
          block.call(model[id])
        end
      end

      def key
        raw.key
      end

      def first(options = {})
        if options[:by]
          sort_by(options.delete(:by), options.merge(:limit => 1)).first
        else
          model[raw.first(options)]
        end
      end

      def [](index)
        model[raw[index]]
      end

      def sort(*args)
        raw.sort(*args).map(&model)
      end

      # Sort the model instances by the given attribute.
      #
      # @example Sorting elements by name:
      #
      #   User.create :name => "B"
      #   User.create :name => "A"
      #
      #   user = User.all.sort_by(:name, :order => "ALPHA").first
      #   user.name == "A"
      #   # => true
      def sort_by(att, options = {})
        options.merge!(:by => model.key("*", att))

        if options[:get]
          raw.sort(options.merge(:get => model.key("*", options[:get])))
        else
          sort(options)
        end
      end

      def delete(model)
        raw.delete(model.id)
        model
      end

      def clear
        raw.clear
      end

      def concat(models)
        raw.concat(models.map { |model| model.id })
        self
      end

      def replace(models)
        raw.replace(models.map { |model| model.id })
        self
      end

      def include?(model)
        raw.include?(model.id)
      end

      def empty?
        raw.empty?
      end

      def size
        raw.size
      end

      def all
        raw.to_a.map(&model)
      end

      alias to_a all
    end

    class Set < Collection
      Raw = Ohm::Set

      def inspect
        "#<Set (#{model}): #{all.inspect}>"
      end

      # Returns an intersection with the sets generated from the passed hash.
      #
      # @see Ohm::Model.find
      # @example
      #   @events = Event.find(public: true)
      #
      #   # You can combine the result with sort and other set operations:
      #   @events.sort_by(:name)
      def find(hash)
        apply(:sinterstore, hash, "+")
      end

      # Returns the difference between the receiver and the passed sets.
      #
      # @example
      #   @events = Event.find(public: true).except(status: "sold_out")
      def except(hash)
        apply(:sdiffstore, hash, "-")
      end

    private

      # Apply a redis operation on a collection of sets.
      def apply(operation, hash, glue)
        target = key.volatile.group(glue).append(*keys(hash))
        model.db.send(operation, target, *target.sub_keys)
        Set.new(target, Wrapper.wrap(model))
      end

      # Transform a hash of attribute/values into an array of keys.
      def keys(hash)
        [].tap do |keys|
          hash.each do |key, values|
            values = [values] unless values.kind_of?(Array) # Yes, Array() is different in 1.8.x.
            values.each do |v|
              keys << model.index_key_for(key, v)
            end
          end
        end
      end
    end

    class List < Collection
      Raw = Ohm::List

      def shift
        if id = raw.shift
          model[id]
        end
      end

      def pop
        if id = raw.pop
          model[id]
        end
      end

      def unshift(model)
        raw.unshift(model.id)
      end

      def inspect
        "#<List (#{model}): #{all.inspect}>"
      end
    end

    class Index < Set
      def apply(operation, hash, glue)
        if hash.keys.size == 1
          return Set.new(keys(hash).first, Wrapper.wrap(model))
        else
          super
        end
      end
    end

    module Validations
      include Ohm::Validations

      # Validates that the attribute or array of attributes are unique. For this,
      # an index of the same kind must exist.
      #
      # @overload assert_unique :name
      #   Validates that the name attribute is unique.
      # @overload assert_unique [:street, :city]
      #   Validates that the :street and :city pair is unique.
      def assert_unique(attrs)
        result = db.sinter(*Array(attrs).map { |att| index_key_for(att, send(att)) }) || []
        assert result.empty? || !new? && result.include?(id.to_s), [attrs, :not_unique]
      end
    end

    include Validations

    class MissingID < Error
      def message
        "You tried to perform an operation that needs the model ID, but it's not present."
      end
    end

    class IndexNotFound < Error
      def initialize(att)
        @att = att
      end

      def message
        "Index #{@att.inspect} not found."
      end
    end

    @@attributes = Hash.new { |hash, key| hash[key] = [] }
    @@collections = Hash.new { |hash, key| hash[key] = [] }
    @@counters = Hash.new { |hash, key| hash[key] = [] }
    @@indices = Hash.new { |hash, key| hash[key] = [] }

    attr_writer :id

    def id
      @id or raise MissingID
    end

    # Defines a string attribute for the model. This attribute will be persisted by Redis
    # as a string. Any value stored here will be retrieved in its string representation.
    #
    # @param name [Symbol] Name of the attribute.
    def self.attribute(name)
      define_method(name) do
        read_local(name)
      end

      define_method(:"#{name}=") do |value|
        write_local(name, value)
      end

      attributes << name unless attributes.include?(name)
    end

    # Defines a counter attribute for the model. This attribute can't be assigned, only incremented
    # or decremented. It will be zero by default.
    #
    # @param name [Symbol] Name of the counter.
    def self.counter(name)
      define_method(name) do
        read_local(name).to_i
      end

      counters << name unless counters.include?(name)
    end

    # Defines a list attribute for the model. It can be accessed only after the model instance
    # is created.
    #
    # @param name [Symbol] Name of the list.
    def self.list(name, model = nil)
      attr_collection_reader(name, :List, model)
      collections << name unless collections.include?(name)
    end

    # Defines a set attribute for the model. It can be accessed only after the model instance
    # is created. Sets are recommended when insertion and retrival order is irrelevant, and
    # operations like union, join, and membership checks are important.
    #
    # @param name [Symbol] Name of the set.
    def self.set(name, model = nil)
      attr_collection_reader(name, :Set, model)
      collections << name unless collections.include?(name)
    end

    # Creates an index (a set) that will be used for finding instances.
    #
    # If you want to find a model instance by some attribute value, then an index for that
    # attribute must exist.
    #
    # @example
    #   class User < Ohm::Model
    #     attribute :email
    #     index :email
    #   end
    #
    #   # Now this is possible:
    #   User.find email: "ohm@example.com"
    #
    # @param name [Symbol] Name of the attribute to be indexed.
    def self.index(att)
      indices << att unless indices.include?(att)
    end

    # Define a reference to another object.
    #
    # @example
    #   class Comment < Ohm::Model
    #     attribute :content
    #     reference :post, Post
    #   end
    #
    #   @post = Post.create :content => "Interesting stuff"
    #
    #   @comment = Comment.create(:content => "Indeed!", :post => @post)
    #
    #   @comment.post.content
    #   # => "Interesting stuff"
    #
    #   @comment.post = Post.create(:content => "Wonderful stuff")
    #
    #   @comment.post.content
    #   # => "Wonderful stuff"
    #
    #   @comment.post.update(:content => "Magnific stuff")
    #
    #   @comment.post.content
    #   # => "Magnific stuff"
    #
    #   @comment.post = nil
    #
    #   @comment.post
    #   # => nil
    #
    # @see Ohm::Model::collection
    def self.reference(name, model)
      model = Wrapper.wrap(model)

      reader = :"#{name}_id"
      writer = :"#{name}_id="

      attribute reader
      index reader

      define_memoized_method(name) do
        model.unwrap[send(reader)]
      end

      define_method(:"#{name}=") do |value|
        instance_variable_set("@#{name}", nil)
        send(writer, value ? value.id : nil)
      end

      define_method(writer) do |value|
        instance_variable_set("@#{name}", nil)
        write_local(reader, value)
      end
    end

    # Define a collection of objects which have a {Ohm::Model::reference reference}
    # to this model.
    #
    #   class Comment < Ohm::Model
    #     attribute :content
    #     reference :post, Post
    #   end
    #
    #   class Post < Ohm::Model
    #     attribute  :content
    #     collection :comments, Comment
    #     reference  :author, Person
    #   end
    #
    #   class Person < Ohm::Model
    #     attribute  :name
    #
    #     # When the name of the reference cannot be inferred,
    #     # you need to specify it in the third param.
    #     collection :posts, Post, :author
    #   end
    #
    #   @person = Person.create :name => "Albert"
    #   @post = Post.create :content => "Interesting stuff", :author => @person
    #   @comment = Comment.create :content => "Indeed!", :post => @post
    #
    #   @post.comments.first.content
    #   # => "Indeed!"
    #
    #   @post.author.name
    #   # => "Albert"
    #
    # *Important*: please note that even though a collection is a {Ohm::Set Set},
    # you should not add or remove objects from this collection directly.
    #
    # @see Ohm::Model::reference
    # @param name      [Symbol]   Name of the collection.
    # @param model     [Constant] Model where the reference is defined.
    # @param reference [Symbol]   Reference as defined in the associated model.
    def self.collection(name, model, reference = to_reference)
      model = Wrapper.wrap(model)
      define_method(name) { model.unwrap.find(:"#{reference}_id" => send(:id)) }
    end

    def self.to_reference
      name.to_s.gsub(/([a-z\d])([A-Z])/, '\1_\2').downcase.to_sym
    end

    def self.attr_collection_reader(name, type, model)
      if model
        model = Wrapper.wrap(model)
        define_memoized_method(name) { Ohm::Model::const_get(type).new(key(name), model, db) }
      else
        define_memoized_method(name) { Ohm::const_get(type).new(key(name), db) }
      end
    end

    def self.define_memoized_method(name, &block)
      define_method(name) do
        instance_variable_get("@#{name}") ||
          instance_variable_set("@#{name}", instance_eval(&block))
      end
    end

    def self.[](id)
      new(:id => id) if exists?(id)
    end

    def self.to_proc
      Proc.new { |id| self[id] }
    end

    def self.all
      @all ||= Ohm::Model::Index.new(key(:all), Wrapper.wrap(self))
    end

    def self.attributes
      @@attributes[self]
    end

    def self.counters
      @@counters[self]
    end

    def self.collections
      @@collections[self]
    end

    def self.indices
      @@indices[self]
    end

    def self.create(*args)
      model = new(*args)
      model.create
      model
    end

    # Search across multiple indices and return the intersection of the sets.
    #
    # @example Finds all the user events for the supplied days
    #   event1 = Event.create day: "2009-09-09", author: "Albert"
    #   event2 = Event.create day: "2009-09-09", author: "Benoit"
    #   event3 = Event.create day: "2009-09-10", author: "Albert"
    #
    #   assert_equal [event1], Event.find(author: "Albert", day: "2009-09-09")
    def self.find(hash)
      all.find(hash)
    end

    def self.encode(value)
      Base64.encode64(value.to_s).gsub("\n", "")
    end

    def initialize(attrs = {})
      @_attributes = Hash.new { |hash, key| hash[key] = read_remote(key) }
      update_attributes(attrs)
    end

    def new?
      !@id
    end

    def create
      return unless valid?
      initialize_id

      mutex do
        create_model_membership
        write
        add_to_indices
      end
    end

    def save
      return create if new?
      return unless valid?

      mutex do
        write
        update_indices
      end
    end

    def update(attrs)
      update_attributes(attrs)
      save
    end

    def update_attributes(attrs)
      attrs.each do |key, value|
        send(:"#{key}=", value)
      end
    end

    def delete
      delete_from_indices
      delete_attributes(attributes)
      delete_attributes(counters)
      delete_attributes(collections)
      delete_model_membership
      self
    end

    # Increment the counter denoted by :att.
    #
    # @param att [Symbol] Attribute to increment.
    def incr(att)
      raise ArgumentError, "#{att.inspect} is not a counter." unless counters.include?(att)
      write_local(att, db.incr(key(att)))
    end

    # Decrement the counter denoted by :att.
    #
    # @param att [Symbol] Attribute to decrement.
    def decr(att)
      raise ArgumentError, "#{att.inspect} is not a counter." unless counters.include?(att)
      write_local(att, db.decr(key(att)))
    end

    def attributes
      self.class.attributes
    end

    def counters
      self.class.counters
    end

    def collections
      self.class.collections
    end

    def indices
      self.class.indices
    end

    def ==(other)
      other.kind_of?(self.class) && other.key == key
    rescue MissingID
      false
    end

    # Lock the object before executing the block, and release it once the block is done.
    def mutex
      lock!
      yield
      self
    ensure
      unlock!
    end

    def inspect
      everything = (attributes + collections + counters).map do |att|
        value = begin
                  send(att)
                rescue MissingID
                  nil
                end

        [att, value.inspect]
      end

      "#<#{self.class}:#{new? ? "?" : id} #{everything.map {|e| e.join("=") }.join(" ")}>"
    end

    # Makes the model connect to a different Redis instance.
    #
    # @example
    #
    #   class Post < Ohm::Model
    #     connect :port => 6380, :db => 2
    #
    #     attribute :body
    #   end
    #
    #   # Since these settings are usually environment-specific,
    #   # you may want to call this method from outside of the class
    #   # definition:
    #   Post.connect(:port => 6380, :db => 2)
    #
    def self.connect(*options)
      self.db = Ohm.connection(*options)
    end

  protected

    def key(*args)
      self.class.key(id, *args)
    end

    # Write attributes using MSET
    def write
      unless attributes.empty?
        rems, adds = attributes.map { |a| [key(a), send(a)] }.partition { |t| t.last.to_s.empty? }

        db.del(*rems.flatten.compact) unless rems.empty?
        db.mapped_mset(adds.flatten)  unless adds.empty?
      end
    end

    def self.const_missing(name)
      wrapper = Wrapper.new(name) { const_get(name) }

      # Allow others to hook to const_missing.
      begin
        super(name)
      rescue NameError
      end

      wrapper
    end

  private

    # Provides access to the Redis database. This is shared accross all models and instances.
    def self.db
      Ohm.threaded[self] || Ohm.redis
    end

    def self.db=(connection)
      Ohm.threaded[self] = connection
    end

    def self.key(*args)
      Ohm.key(*args.unshift(self))
    end

    def self.exists?(id)
      db.sismember(key(:all), id)
    end

    def initialize_id
      self.id = db.incr(self.class.key("id")).to_s
    end

    def db
      self.class.db
    end

    def delete_attributes(atts)
      atts.each do |att|
        db.del(key(att))
      end
    end

    def create_model_membership
      db.sadd(self.class.key(:all), id)
    end

    def delete_model_membership
      db.srem(self.class.key(:all), id)
    end

    def update_indices
      delete_from_indices
      add_to_indices
    end

    def add_to_indices
      indices.each do |att|
        next add_to_index(att) unless collection?(send(att))
        send(att).each { |value| add_to_index(att, value) }
      end
    end

    def collection?(value)
      self.class.collection?(value)
    end

    def self.collection?(value)
      value.kind_of?(Enumerable) &&
      value.kind_of?(String) == false
    end

    def add_to_index(att, value = send(att))
      index = index_key_for(att, value)
      db.sadd(index, id)
      db.sadd(key(:_indices), index)
    end

    def delete_from_indices
      (db.smembers(key(:_indices)) || []).each do |index|
        db.srem(index, id)
      end

      db.del(key(:_indices))
    end

    def read_local(att)
      @_attributes[att]
    end

    def write_local(att, value)
      @_attributes[att] = value
    end

    def read_remote(att)
      unless new?
        value = db.get(key(att))
        value.respond_to?(:force_encoding) ?
          value.force_encoding("UTF-8") :
          value
      end
    end

    def read_locals(attrs)
      attrs.map do |att|
        send(att)
      end
    end

    def read_remotes(attrs)
      attrs.map do |att|
        read_remote(att)
      end
    end

    def self.index_key_for(att, value)
      raise IndexNotFound, att unless indices.include?(att)
      key(att, encode(value))
    end

    def index_key_for(att, value)
      self.class.index_key_for(att, value)
    end

    # Lock the object so no other instances can modify it.
    # This method implements the design pattern for locks
    # described at: http://code.google.com/p/redis/wiki/SetnxCommand
    #
    # @see Model#mutex
    def lock!
      until db.setnx(key(:_lock), lock_timeout)
        next unless lock = db.get(key(:_lock))
        sleep(0.5) and next unless lock_expired?(lock)

        break unless lock = db.getset(key(:_lock), lock_timeout)
        break if lock_expired?(lock)
      end
    end

    # Release the lock.
    # @see Model#mutex
    def unlock!
      db.del(key(:_lock))
    end

    def lock_timeout
      Time.now.to_f + 1
    end

    def lock_expired? lock
      lock.to_f < Time.now.to_f
    end
  end
end